Storing a sputum sample

Storage conditions of sputum sample can effect the test results.

• Sputum samples should be transported to the laboratory as soon as possible after collection.
• It is the responsibility of Laboratory Technician (LT) and Senior TB Laboratory Supervisor (STLS) to ensure proper storage and transport of sputum specimens.
• Sputum is stored to preserve the specimen quality.
• The stored sputum samples should not be frozen.

Storage of Sputum Samples

For microscopy

• For smear microscopy, sputum specimens should be examined on the same day and not later than 2 days after collection.
• If delay is unavoidable, the sputum collected should be stored in a cool place/ refrigerated at 4°C to inhibit the growth of unwanted microorganisms.
• Stored sputum samples should be protected from light and heat to prevent liquefaction of the sample, else it makes the selection of mucopurulent part of the sample difficult.
• Samples received over holidays/weekends should be stored in a cool place/ refrigerated at 4°C.

For liquid culture

• Sputum should be stored in a cool place/ refrigerated at 4°C to inhibit the growth of unwanted microorganisms; not later than 3 days after collection.

For molecular tests - Nucleic Acid Amplification Test (NAAT) and Line Probe Assay (LPA)

• Sputum must be stored by refrigerating at 4°C to inhibit the growth of unwanted microorganisms and transported in cool chain to the nearest molecular laboratory. It should not be stored beyond one week at 4°C.

Resources

Technical and Operational Guidelines; Chapter 3: Case finding and diagnosis strategy

PMDT Guidelines 2021

Assessment